A stereocontrolled synthesis of (.+-.)-emetine and (.+-.)-protoemetinol by intramolecular michael reaction.

Abstract

An intramolecular Michael reaction of 9 stereoselectively gave the tricyclic compound (10), which was converted to (±)-protoemetinol (2) and 13. Compound 13 is an important intermediate for the synthesis of (±)-emetine. A simpler preparation of 13 was also carried out by the intramolecular Michael reaction of 14, followed by reduction of the ketone moietv. Furthermore, the stereoselective formation of 26, which is an intermediate for the synthesis of (±)-emetine, was achieved by the floowing sequence of reactions : intramolecular Michael reaction, of the ketone moiety, and removal of the N-carbomethoxy group.